Screens which may be used as a sieve screen and/or a filter screen are generally comprised of a plurality of openings or open spaces which may be produced in a variety of known ways such as being in the form of fabric comprised of woven, interlaced or intertwined thread, cord or wire, or may be molded, stamped, needled, etched and the like, for forming a gauze or mesh material which can be used for separating coarse and fine particles from each other, or for removing particulate or viscous matter from fluids, including liquids and/or gases. The current state of the art for such screens usually involves the use of a cloth, or felt, or other form of edging which is typically attached by sewing or stitching such edging to the perimeter of the perforated or mesh portion for providing a friction surface to preclude the screen from slipping out from under a clamping ring or other type of holding attachment. Also, such edging typically provides some degree of finished appearance to the screen and additionally may have a gasketing function. Such a prior art screen is shown in FIGS. 1 and 2 and will hereinafter be further described.
There are a considerable number of problems which are typical of such prior art screens:
(a) Current cloth or felt edging materials absorb liquids. Washing and drying of conventional screens is made difficult because of this tendency for present edgings to absorb liquids. PA1 (b) Conventional sewn-on edgings have gaps or crevices which can trap either particles or liquids, or both. Cleaning of such screens for reuse is difficult and cross-contamination between process batches is a distinct possibility. PA1 (c) Conventional sewn-on edgings can be, and usually are, costly because of waste of the edging material. The "donut" of cloth used for the typical circular, oval or rectangular edging is often die cut out of a roll of fabric. The unused center portion is usually discarded, thus resulting in a waste factor as high as 60 percent. PA1 (d) Conventional sewn-on edgings require the use of ink markings for identification, such as for specifying indicated uses, precautions, sizes, models, and other forms of information. The ink used for marking may be a source of contamination in certain process applications.
United Kingdom Patent 482,622 discloses a filtration device comprised of a wire gauze or mesh having a pair of peripheral gasket members of india rubber disposed on opposite marginal edges thereof and then vulcanized to form a continuous coating intimately bonded to the wire gauze. There is no teaching of patterned or intermittent indicia nor discontinuous portions for allowing electrical contact for grounding of the screen, nor teaching of providing informative data and the like to the screen area or marginal portions thereof.
U.S. Pat. No. 3,382,985 discloses a filter element in the form of a woven cloth of polypropylene, nylon, Acrilon or polyurethane fiber, fiber glass or cotton with an integral gasket which eliminates gasket grooves. The gasket material may also consist of woven polymeric fibers using a resilient or spongy, e.g., waffle, trilock or honeycomb bonded with an adhesive, e.g., epoxy adhesive, liquid neoprene or latex. The gasket may also be sewn to the filter element with polymeric thread. The gasket material is continuous throughout and the patent does not teach or suggest a discontinuous coated edge portion nor indicia of any kind..
U.S. Pat. No. 3,332,557 discloses a filter element comprising a wire mesh screen and a peripheral or marginal anchoring strip of greater thickness than the wire mesh. The gasket portion is disclosed as being in the form of a molded ring, which may be rubber or the like. As in the above mentioned prior art, there is no teaching or suggestion of a discontinuous polymeric coated edge which would allow for electrical grounding nor for the provision of indicia of any kind.